Aegon IV legitimized all his bastard's, including Daemon Blackfyre, on his deathbed. In fact, it was rumored Aegon IV's heir was not really his son, but had been fathered by Aegon's brother. 2)Daemon was pure blooded Targaryen only having a bastard name because his mother was not married to the king. This was signifiant for two reasons: 1)The sword Blackfyre had been passed down to all the Targaryen kings since their invasion of Westeros, it was the sword of kings. House Blackfyre was born the day King Aegon IV gave his bastard son, Daemon Waters, the Valyrian steel sword Blackfyre.
Help out the alliance and it's bannermen.'As Blackfyre sweeps over Westeros, all that remains will be Ashes and Bones'